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Old 08-28-2009, 08:47 PM   #1
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'99 Brake Rotor issue

Ok, Ok maybe this is a dumb question, but I don't seem to be able to find the answer. I have searched around and I know that the 1999 wrangler has different size front brake rotors depending on when it was built that year. I know that if you get the wrong size it may be too big and lock up your front end, but none of the threads I found are cut and dry and tell what the two sizes are so I know if I have the larger or smaller size.


Can someone please tell me what exactly to measure on my rotors and what size is the "larger" and what size is the "smaller" size so that I know what to buy. I prefer not to find out by installing the wrong rotors........

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Old 08-28-2009, 09:04 PM   #2
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I cannot tell you what size you have, But I can tell you about my exp. I have a 2000 sahara. I decided to put new rotors on when i replaced the pads. I purchsed them at the local auto store. I went home put them on, placed the pads in the calibers and put everything back together. As I was tightening the lugs on the wheel, I noticed the wheel starting to freeze up (not turn freely) I did not think much of it. I tightened up all the lugs on both sides. I went to put the jeep in reverse, The front wheels were LOCKED! I went to loosen up the lugs, and could'nt. They would not budge. After about an hour of breaking pipes and wrenches to get them loose, I went to lowes and purchased an electric impact wrench. That worked great. I then proceeded to take everything apart and brought the rotors back. The kid said "that's the part # that's called for. He even showed me the comp. But the rotors did not match. There was a difference in size of about 1/8 inch. We proceeded to go through the rotors he had to match one of the same size. Turned out the rotors for my jeep are the one's used on the cherokee's. That's how I found out about this issue.

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Old 08-28-2009, 09:13 PM   #3
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Thanks for the reply daanbc, I had actually read your post when I was looking around for some information. I am trying to avoid that same issue.

I have actually found a brake website that asks if I want 82mm or 78mm rotors when I type in 1999 jeep wrangler. So hopefully those are the two sizes I am looking for......

Where exactly would I take that measurement to know what size I have?
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Old 08-29-2009, 06:28 AM   #4
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It was the hight. When the rotor's were place upside down laying down one sat higher then the other.
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Old 08-29-2009, 06:58 AM   #5
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I've never heard of this before! So your looking at the back spacing on the rotor! Why do car companies do that crap?
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Old 08-29-2009, 10:07 AM   #6
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I've never heard of this before! So your looking at the back spacing on the rotor! Why do car companies do that crap?
I believe 99 and 00 were years where changes occured. So while the plant's was producing the jeeps, they were making changes.
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Old 08-29-2009, 10:19 AM   #7
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Here is what I know ,difference is about 3/16th. I recall compsite vs fully cast as well. I also recall the hubs where different as well, hence the reason for the rotors. Cast is 1pc composite looks like 2pc. Been a while since I had to deal with it.
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Old 08-29-2009, 11:02 AM   #8
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Thanks for the info daanbc, it was the height of the rotor like you said. Mine are 78mm.


FYI, the website I spoke of earlier was brakeplanet.com, and they were the ones that ask if it was either 78mm or 82mm.
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Old 08-29-2009, 11:21 AM   #9
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Thanks for the info daanbc, it was the height of the rotor like you said. Mine are 78mm.


FYI, the website I spoke of earlier was brakeplanet.com, and they were the ones that ask if it was either 78mm or 82mm.
Gald that I could help out someone on this forum. I know I been helped alot.!!
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Old 08-29-2009, 11:32 AM   #10
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Remove one of your old rotors and take it with you when you go to buy rotors. About the only way to know for sure you're getting the right model is to lay your old rotor flat on the counter with the new one next to it. Lay a straight-edge across them to make sure they'e the exact same height. I wouldn't trust any other method.
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Old 09-10-2011, 12:50 PM   #11
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Whats up with the rotor part #'s on my '99?? - JeepForum.com

here i remember reading this on jeep forums, it may not help but good luck i have to do same thing here soon
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Old 09-10-2011, 02:00 PM   #12
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Old 09-10-2011, 10:12 PM   #13
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Old 09-11-2011, 09:39 AM   #14
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I've yet to see anyone at the parts stores who understands fully what the issue is and how to measure the rotors correctly.

The problem lies in there being composite and full cast rotors used in the same year as well as two different heights for the different unitbearings.

The composite rotor has a very thin hat shell, so if you measure the overall height, a taller inside depth early rotor can get very close to the same overall height of the later full cast with an overall shorter depth but with a much thicker hat.

The only dimension that matters is the depth from the inside of the hat to the inboard face of the rotor so it will match the unitbearing height.

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